The federal lawsuit against Jackson, spearheaded by two nonprofit legal groups, is a prong in a nationwide fight over how poor people should be treated by the criminal justice system.

Similar suits have been filed in Alabama, Louisiana and Missouri. All accuse court systems of ignoring U.S. Supreme Court decisions that say courts must determine whether people have the ability to pay fines before jailing them for nonpayment. The lawyers say indigent people must be offered a chance to perform community service or else jail equals a “debtors’ prison.”

“This is not about giving people a free pass or giving poor folks a get-out-of-jail-free card,” said Cliff Johnson, a lawyer for the MacArthur Justice Center. “This is about not punishing people for the fact that they’re poor, in a way other people don’t experience.”

Mississippi law already states, “The defendant shall not be imprisoned if the defendant is financially unable to pay a fine.” It was affirmed in a 1984 state Supreme Court decision.

All of the plaintiffs owed at least $1,200 in fines and fees. The lawyers said none had a job or any significant assets when they were arrested. All faced orders to pay at least 65 percent of fines immediately or be jailed at the Hinds County Detention Center or the Hinds County Penal Farm. There, inmates can “work off” their debt at $58 a day, or be credited at $25 a day if they can’t or won’t work.

The plaintiffs ask that the city be barred from jailing people without checking defendants’ ability to pay. They also want a ban on forcing people to work while in jail. The suit also asks a judge to order the city to pay damages to people who were jailed.

The city released a statement saying it had been talking to the lawyers about their concerns, but will now “vigorously defend against these unfounded claims.”

“The city of Jackson does not operate a ‘debtor’s prison,” and aims to treat all of its citizens fairly under the law,” the statement says. “The city of Jackson does not imprison any citizen without statutory authority and the weighing of all factors.”

The suit, filed Friday, says the lead plaintiff, 58-year-old Jerome Bell, was arrested in July and told to pay $4,759 or go to jail. The suit says Bell slept on the concrete floor of a booking cell at the Hinds County Detention Center, and was credited at a rate of only $25 a day because his disabilities meant he couldn’t work at the county farm.

Lawyers persuaded a judge to release Bell and sentence him to community service. But because the city offered no service program that didn’t involve physical labor, the judge then ordered Bell to pay $25 a month toward his fine.